This week is the highly anticipated Supernatural TV parody
episode "Changing Channels." Previews have already shown that the
episode will feature Sam and Dean living in various TV show parodies,
including a traditional sitcom and CSI. But perhaps the funniest is a spot-on parody of Supernatural's time slot rival, Grey's Anatomy.

I was fortunate enough to see an early copy of "Changing Channels," and
without giving away too many details, there's more to this episode than
just parodies. Like all of the best Supernatural episodes, the
comedic elements are only a small part of the overall story, and there
are definitely some shocking twists and dramatic moments in store for
all the characters. Read my early review of this episode.

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Some Supernatural fans have probably never seen an episode of Grey's Anatomy, and if not, some of the specific jokes may go over your head. To help you out, I've compiled a list of five things about Grey's Anatomy you should know before going into this episode of Supernatural.

1. "Seriously."

This word has become a de facto catch phrase for Grey's Anatomy, with characters using it all the time to emphasize their points. During season 2, "Seriously" developed a mind of its own, and if you play the drinking game (take a shot every time someone uses the word), you're guaranteed to be wasted within 10 minutes of every Grey's Anatomy episode.

2. Ellen Pompeo as Meredith Grey

Ellen Pompeo plays the lead role of Meredith Grey, a dark and often depressed doctor who falls in love with a resident. The two have a very rocky romantic history, breaking up and getting back together multiple times per season.

3. Sandra Oh as Cristina Yang

Meredith's best friend is Dr. Yang, a cut-throat, hardcore heart specialist who strives to be the best and typically comes across as robotic and emotionless.

4. Izzie and Denny

At the end of season 2, Dr. Izzie Stevens fell in love with a patient named Denny Duquette who was waiting for a heart transplant. She infamously cut his LVAD wire in order to put him at the top of the donor list, but through a complicated set of circumstances, Denny died. Since that moment, Denny has made numerous return appearances as a ghost. In an additional Supernatural tie-in, Denny was played by Jeffrey Dean Morgan, Sam and Dean's dead dad John.

5. The Seattle Grace-Mercy West Merger

This season on Grey's Anatomy, the hospital where the show is set, Seattle Grace, merged with a rival hospital, Mercy West, forcing the two to work together.

Keep all of this information in mind when you watch Supernatural this week, because it will help make the jokes even funnier. Supernatural airs Thursday at 9pm on the CW.